Methods for the design and testing of digital systems

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The major area of study concerns the design and uses of Finite State Machines as generators to build onto a chip to provide built-in self-testing of the system on the chip. We have proposed Cellular Automata Registers (CAR) as alternatives to linear feedback shift registers in a number of applications, since, while they are similar to linear feedback shift registers from a theoretical perspective, they generate bit sequences that lead to improved testing behaviour. Our earlier work has led to the only practical algorithm for the synthesis of these machines. However, it is clear that modifying them to be slightly non-linear, gives improved performance for testing. The design and analysis of such machines is considerably more complex, since we lack some of the analytical tools, and the proposed research will continue both with the development of CAR and underlying research into other non linear machines. Our second direction is a new one developed over the last year in the area of reversible logic.  It picks up on some of our earlier work from 25 years ago on restricted primitives for the design of circuits. This are has become of rapidly increasing importance rcently because of the von Neumann/Landauer principle that normal (non reversible) logic operations incur a fundamental minimum energy cost. This cost threatens to end improvements in practical computer performance within the next 15 to 20 years. However, it has been proved that computers based on reversible logic operations can reuse a fraction of the signal energy (in theory, this fraction can approach 100%) that gives us the possibility of continuing to arbitrarily improve computer performance within a specified level of power dissipation. For this to be feasible, we have to develop algorithms for the design and testing of highly optimized reversible logic circuits. This is the goal of our second research area.